I'm in the planning stage of building a wind tunnel, and I think I have it about down - except for one "minor" detail. How do I make the air that is passing through my wind tunnel visible, so that I can see how aerodynamic the things that I'm testing are? Does smoke work for this?

if you used a high powered smoke 'launcher' (can't think of the right word) it would probably work

 

although quite what they use in wind tunnels i do not know, its high powered and in a thin jet.

Look here - http://www.aerorocket.com/offer.html

 

They use smoke - they also use very fine filaments.

Thanks, that'll help a lot.

For a brief moment I was going to say use some fine baking flour in there, but then I realized that it would be a pretty major fire/explosion hazard if you did.

Sounds like a barrel-o-fun!

 

:-D

 

It prbably wouldn't be too large of an issue, because I'm doing this outsicde (I'd rather not have the whole house smell sike smoke or whatever I put in the wind tunnel).

 

And I've definitely done more dangerous things than fill a box type thing with very fine particles of flour dispersed in the air. But caution is always good.

It appears to smoke as it evaporates - how about using that?

It'd probably be easier to get a hold of smoke than to use the sublimation process of dry ice.

 

How expensive is dry ice, anyway?

not verry.. but for my band we use smoke efects that u can get at party city or reely ne where that would be good to use.. i also know that there are colored dyes you can use that evaporate for those smoke machiens

what are you testing in this wind tunnle?

It's not the dry ice that is smoking. It's that the CO2 sublimating off of it is so cold that it causes any water in the air to immediately condense, so the 'smoke' you see is just water. If you have super dry air, then you will see no "smoke".

Huh. I knew it was sublimation, but I never knew that the fog/"smoke" was water crystals. It makes perfect sense, though. Just like your breath during winter.

Just like your breath during winter.

 

 

100% correct!

Fake - I'm using the windtunnel to test propellers/impellers, aerodynamics in body design, and airfoil efficiency, among other things, in order to build a very efficient hovercraft.

 

[EDIT: It's NOT for a school project - it's something I work on in my "free time," which, seeing as today is a semi-regular school day and I just got home for the first time after 15 hours of being at school, is NOT MUCH.]

A water tunnel will work just like a wind tunnel if you want to test aerodynamics. If you wish to use a windtunnel, install a smoke system. In many pics you see about aerodynamics testing you see these really fine lines of smoke. No idea how they got that perfect smoke tho.

Water tunnels, I never even thought of that... How might one go about making the flow visible, though? I could think of some ways, but noting practical.

a crystal of potassium permanganate will leave a very visible purple/violet trail.

 

you can then clarify the water later with a drop of Iron Sulphate afterwards